Fiberglass can be used in a variety of thermal insulation applications including, for example, building insulation, pipe insulation, and in molded automobile parts (e.g., hood liners), as well as in a variety of acoustical insulation applications including, for example, molded automobile parts (e.g., hood and dashboard liners) and office furniture/panel parts. A general discussion of fiberglass manufacturing and technology is contained in Fiberglass by J. Gilbert Mohr and William P. Rowe, Van Nostrand Reinhold Company, New York 1978, the disclosure of which is hereby incorporated herein by reference.
Fiberglass insulation products traditionally include matted glass fibers that are bonded together by a cured thermoset binder prepared from resole resin. Resole resin is a phenol-aldehyde resin having a molar ratio of phenol to aldehyde of about 1:1.1 to about 1:5. Preferably, the phenol to aldehyde ratio is from about 1:2 to about 1:3. The phenol component of the resole resin can include a variety of substituted and unsubstituted phenolic compounds. The aldehyde component of the resole resin is preferably formaldehyde, but can include so-called masked aldehydes or aldehyde equivalents, such as acetals or hemiacetals. Specific examples of suitable aldehydes include: formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, furfuraldehyde, and benzaldehyde.
Highly alkaline phenol-formaldehyde (PF) resole resins, as well as phenol-formaldehyde resole resins extended with urea (PFU resins), are used in conventional processes, and have been relied on heavily over the past several years to prepare PF and PFU binders, respectively, for fiberglass insulation products. Though PFU binders are more cost-effective than PF binders and provide cured fiberglass insulation products with the desired physical properties (e.g., rigidity, tensile strength, water absorption), PFU binders may exhibit some loss in thermosetting properties as the urea content increases. Further, the resulting cured products may have high free formaldehyde and/or high trimethylamine content, as well as a distinctive or unpleasant odor (owing to the presence of formaldehyde and/or trimethylamine, the latter a byproduct of scavenging formaldehyde with urea), that may limit the use of PFU binders in certain applications.
Accordingly, efforts have been made to incorporate other resins and/or additives into PFU binders that can enhance, or at least not diminish, the desired properties of the resulting binders, while also lowering formaldehyde and/or trimethylamine emissions from bonded fiberglass insulation products.